Pulse modulation signaling system



May 17, 1949. c; w. HANsl-:LL 2,470,698

PULSE MODULATION SIGNALING SYSTEM Original Filed June 24, 1942TM/vM/TTE/P F/Pfana. PULSE /VMPL I uff 5% f2 D an@ if 5E f :i 1| a =|LIl ljL f1 4I @ai f2 l l 1 l namur/av l IIS/P07' INVENTOR ay m' ATTORNEYPatented May 17, 1949 2,470,698 PULSE MDULATION SIGNALING SYSTEMClarence W. Hansell, Port Jefferson, N. Y., assignor to RadioCorporation of America, a corporation of Delaware Application August 30,1945, Serial No. 613,512, which is a division of application Serial No.448,223, June 24, 1942. Divided and this application May 13, 1947,Serial No. 747,826

s claims. (c1. 332-14) The present invention relates to a signalingcommunication system employing electrical pulses, and is a division ofmy copending application Serial No. 613,512, filed August 30, 1945, nowU. S. Patent 2,424,274, granted July 22, 1947, in turn, a division of myapplication Serial No. 448,223, filed June 24, 1942, now U. S. Patent2,389,432 granted November 20, 1945.

Briefly stated, the present invention resides in the use of a novelsystem wherein short highpower pulses are delivered by the transmitterto a transmission medium. Intelligence is conveyed by a series of pulseswhich are modulated in phase or frequency in accordance with acharacteristic of the modulations to be transmitted.

The communication system of the invention, employing short high-powerpulses, has both mili- 'tary and civilian uses and possesses thefollowing advantages among others; (1) A higher peak power can betransmitted than obtainable by the customary type of continuous wavetransmitter equipment; (2) the system of the invention is very hard tointerfere with, consequently the procedure known as jamming by an enemyin time of war has reduced effect; (3) by making the receiver of theinvention operate synchronously with the transmitter, or by using anadjustable threshold system in addition to limiting, it is possible toreceive transmitted pulse signals despite extraneous and undesirableearth potentials; and (4) the signals may be demodulated at the receiverwithout the necessity of inserting any xed marker pulses.

The following is a more detailed description of the inventionaccompanied by a drawing Whose single figure illustrates the improvedpulse type transmitter of the invention.

Referring to the drawing, I have shown a frequency modulated pulseoscillator and amplifier comprising double element vacuum tube ampliiler2|. One part of tube 2| is provided with regenerative feedbacktransformer T2 and the time constant circuit made up of resistance R1and condenser C1. 'I'he resistance R2 and condenser Cz provide a gridbias to the control electrode of the oscillator part of tube 2| and, ifdesired, may provide a time constant such as to contribute to thefrequency of pulse oscillation.

The left hand portion of tube 2| constitutes the generator side, whilethe right hand portion of tube l2| is the amplifier side for the pulsesproduced in the generator side. Tube 22 is an amplifier which amplifiesthe output from the ampllfier side of tube 2 I. The output fromamplifier 22 is passed through transformer Ta to the ground connectionsE, E. 'I'he primary and secondary windings of transformer T3 areadjustable, as shown, to obtain the proper impedance match to theconnecting circuits.

In the operation of the system of the invention, the oscillatorelectrode structure of tube 2| receives anode potential by the chargingof condenser Ci through resistance R1. When the anode potential riseshigh enough, anode current starts, causing transformer T2 to push theoscillator control electrode momentarily positive, thereby caus'g arapid discharging of condenser C1 and a charging of condenser C2. Theanode current then cuts o, leavingthe anode potential low and controlelectrode bias potential high. Then, after a time, the bias potentialdecreases by leakage of charge from condenser C2 through resistance R2,while the anode potential rises by charging of condensery C1 throughresistance R1, ending in another pulse of anode and grid current. Thisprocess repeated at rapid intervals (say at a rate of 20,000 pulses persecond, with the pulses very short compared to the time intervalslbetween them) provides-the pulse oscillation. The pulses produced bythe generator or oscillator side of tube 2| are D. C. pulses ofconstantwidth as distinguished from pulses or .bursts of alternatingcurrent.

To modulate the frequency of the pulse oscillation, a. modulatingpotential is applied through transformer T1 and the parallel combinationof resistance R2 and condenser C2. This causes a variation or modulationin the oscillator grid bias potential which causes anode current tostart at variable time intervals following preceding pulses and therebymodulates the pulse frequency. It will be apparent from the foregoingthat there is no modulation of a carrier but rather a modulation of therate of occurrence of the D. C. pulses produced lby the pulseoscillator.

The modulation may, as an example, comprise voice frequencies rangingfrom say 150 to 3000 cycles per second, and may be of such an amplitudeas to modulate the pulse frequency by a maxy imum of plus and minus 3000to 6000 cycles per second.

The frequency modulated pulses are amplified in the amplifier portion oftube 2| and again in tube 22 from which relatively high power pulses aredelivered to the spaced ground connections E, E' through impedanceadjusting transformer T3. The resulting pulses constitute a series ofconstant width pulses which are modulated in phase or frequency, thetime interval between the pulses varying in accordance with themodulations to be transmitted.

What is claimed is:

1. A pulse modulation signalling system comprising a vacuum tube pulsingoscillator electrode structure, connections for causing `said oscillatorto periodically produce pulses of energy, said connections including aregenerative feedback transformer and a time constant circuit made up ofa resistor and a capacitor, the bias potential for said oscillator beingdetermined by the charge on said capacitor and the value of saidresistor through which said charge leaks off, and a. source ofmodulation coupled to the oscillator for varying the bias, to therebymodulate the pulse frequency.

2. A pulse modulation signalling system comprising a pulse oscillatorhaving an electric discharge device provided with an anode, a cathodeand a grid, a regenerative feedback transformer having rst and secondwindings, a connection from one terminal of said first winding to saidanode, a connection from another terminal of said rstwinding to saidcathode through a condenser, a D. C. connection from said last terminalto the positive side of a source of unidirectional potential through aresistor, a D. C. connection from said cathode to the negative side ofsaid source of unidirectional potentialfa connection from one terminalof said second Winding to said grid, a source of modulation, a,connection from one terminal of said source of modulation to saidcathode, a connection from another terminal of said source of modulationto another terminal of said second winding through a condenser, aresistor in shunt to said last condenser, and an output circuit coupledto one of said windings.

3. A pulse modulation signalling system comprising a pulse oscillatorhaving an electric discharge device provided with an anode, a cathodeand a grid, a regenerative feedback transformer having first and secondwindings, a connection from one terminal of said first winding to saidanode, a connection from another terminal of said rst winding to saidcathode through a condenser, a D. C. connection from said last terminalto the positive side of a source of unidirectional potential through aresistor, a D. C. connection from said cathode to the negative side ofsaid source of unidirectional potential, a. connection from one terminalof saidsecond winding to said grid, a source of modulation, a connectionfrom one terminal of said source of modulation to said cathode, aconnection from another terminal of said source of modulation to anotherterminal of said second winding through a. condenser, an amplifierprovided with an anode. a cathode and a grid, direct connections betweenthe grids and cathodes respectively, of said ampliiler and oscillator, aresistive connection between the anode of said amplifier and thepositive side of said source ofunidirectional potential, a condenserconnecting said resistive connection and said cathodes, and a pulseamplier coupled to the anode of said first amplifier.

4. A pulse modulation signalling system comprising a vacuum tubeoscillator provided with an anode, a cathode and a control grid,connections including a time constant circuit of resistance andcapacitance for periodically varying the bias potential on said gridbetween values which permit anode current -to flow and anode current tocut-off, and a source of modulation coupled between said grid andcathode for varying and grid bias potential and thereby cause anodecurrent to start at variable time intervals, to thereby vary the pulseoutput frequency.

5. A pulse modulation system comprising a continuously operating pulsingoscillator provided with connections including a time constant circuitof resistance and capacitance of such values as to cause said oscillatorto produce pulses of energy which are short compared to the timeintervals between them, and a source of modulation of varying audiofrequency coupled to said oscillator for varying the bias on saidoscillator and thereby modulate the occurrence rate of the pulsesgenerated by said oscillator, the pulses generated by said oscillatorhaving a frequency at least twice that of the modulation frequency.

6. A pulse modulation system comprising a continuously operating pulsingoscillator provided Iwith connections including a time constant circuitof resistance and capacitance of such values as to cause said oscillatorto produce pulses of direct current which are short compared to the timeintervals between them, and a source of modulation of varying audiofrequency coupled to said oscillator for varying the bias on saidoscillator and thereby modulate the occurrence rate of the pulsesgenerated by said oscillator.

CLARENCE W. HANSELL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,262,838 Delorae et al. NOV. 18.1941 2,366,307 Anderson Jan. 2, 1945 2,407,860 Wolf l Sept. 17, 1946

